Choosing a Mattress for Side Sleepers

Lie on your side and look at the line of your spine from behind. It should run straight and horizontal, parallel to the mattress. Two things go wrong:

• Too firm — the shoulder cannot sink, so it props you up and your spine bends upward towards the ceiling. You feel it as a sore shoulder, a dead arm, or waking up to change sides all night.
• Too soft — the hip sinks further than the shoulder and the spine sags into a hammock. You feel it as a stiff lower back in the morning.

Side sleepers get this wrong more often than any other position because the received wisdom — "a firm mattress is better for you" — is close to the opposite of what side sleeping needs. Firmness is not virtue. The right mattress is the one that keeps that line straight.

How to check it properly: lie in the position you actually sleep in, for a good ten minutes, not thirty seconds. Then slide a hand into the gap under your waist. A small snug gap is right. If your hand slides through easily the mattress is too firm; if you cannot get a hand in at all, it is too soft.

For side sleepers the question "how firm?" matters less than "what relieves pressure?" — because the goal is a surface that yields locally at the shoulder and hip while supporting everywhere else. Two constructions do that well:

• Memory foam — the strongest pressure relief available, because it moulds around the shoulder and hip rather than pushing back against them. It is also the best at stopping a partner's movement from waking you. The trade-offs are heat retention and a slow response, so turning over takes a little more effort. If you sleep hot, look for a cool-touch comfort layer.
• Pocket sprung — each spring moves independently, so the mattress contours zone by zone instead of as one sheet. That gives you pressure relief and support at the same time, and it sleeps cooler than foam because air moves between the springs. The most reliable all-round starting point, and the largest part of our range.
• Hybrids — a pocket spring unit under a foam comfort layer. In principle the best of both: foam's contouring at the shoulder, springs' airflow and support underneath.

What to avoid: a open coil mattress moves as a single connected unit, so it cannot yield at the shoulder without dipping everywhere. It is a reasonable guest-room mattress and a poor side-sleeper one.

Firmness is felt, not measured — the same mattress feels softer to a heavier person and firmer to a lighter one. As a starting point for side sleeping:

You weigh	Start at	Why
Under roughly 9 stone	Soft	Not enough load to press into a firmer comfort layer, so a firm mattress simply acts as a hard surface
Roughly 9–16 stone	Medium	The usual landing zone for side sleepers — enough give at the shoulder, enough support at the waist
Over roughly 16 stone	Medium-firm	More load compresses the comfort layers further, so a medium can bottom out at the hip

An honest note about our range. Most of the mattresses we stock are built firm, and only about a third of them carry a firmness rating at all — so the firmness filters above will show you a short list rather than the whole catalogue. If you are a side sleeper, you will find more of what suits you by filtering on memory foam or pocket sprung and reading the comfort-layer description, than by relying on the firmness filter alone. We would rather tell you that than send you to an empty page.

If you share the bed and only one of you sleeps on their side, the disagreement is usually better solved with width than with firmness. A King or Super King lets two people sink to different depths without rolling into each other.

This is the cheapest fix on this page and the most overlooked. On your side, the gap between your ear and the outside of your shoulder is the widest gap of any sleeping position — often 12–15 cm. A pillow that suits a back sleeper will let your head drop towards the mattress and bend your neck sideways all night.

• Side sleepers generally need a higher, firmer pillow than back or front sleepers — enough loft to fill the shoulder gap and hold your head square.
• Check it the same way you check the mattress: from behind, your head should be level, not tilted up or drooping down.
• A pillow between the knees keeps the top leg from pulling the pelvis forward and twisting the lower back. It costs very little and helps a lot of people.
• If a new mattress fixed your shoulder but not your neck, the pillow is almost certainly the remaining problem.

We would rather not sell you a mattress that will not help:

• Your base. A sagging divan or a slatted frame with wide or broken slats will undermine any mattress laid on it. A new mattress on a worn base is money wasted.
• Age. Most mattresses lose meaningful support at around seven to eight years, and side sleepers wear a visible hip-and-shoulder dip faster than back sleepers because the load is concentrated. If yours has a dip you can see, that is your answer.
• Adjustment time. Give a correctly chosen mattress two to four weeks. Your body has adapted to whatever it was on before, so the right mattress can feel wrong at first.
• Persistent shoulder pain that does not settle when you change position, or numbness and tingling that travels down the arm, is a matter for a GP or physiotherapist rather than a mattress purchase. Nothing on this page is medical advice.